The dependence of AlN molar fraction of AlGaN in wet etching by using tetramethylammonium hydroxide aqueous solution

We investigated the etching rate of the m-plane of AlGaN by wet etching with tetramethylammonium hydroxide aqueous solutions (25 wt%, 85 °C). After dry etching was performed along the m-plane of AlGaN, wet etching was performed to stably form the m-plane facet of AlGaN. Also, the etching rate increases as the increased AlN molar fraction. In the case of forming a heterojunction such as a UV light-emitting diode, by performing wet etching for 5 min, the flat m-plane facets were formed even though there was a large dependence in AlN molar fraction. These facets were almost vertical and flat with respect to the c-plane, so it has the potential for the use as laser mirror. Also, no change in current density–voltage characteristics was confirmed after the wet etching. Therefore, this method is effective for deep UV laser diode fabrication technology on sapphire substrate.